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92Camaro

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Discussion starter · #1 ·
Mike,
Do you have any experience with a BB Chevy head casting number 702. This is a oval port closed chamber cast iron head. I had the heads cut for the larger valves, 2.19 & 1.88. I'm going to unshroud the chambers (remove about .100 per side) to match the head gasket. The head in stock form with stock valves are supposed to be around 96.4 cc's. How much can you safely flat mill off this head before you get into trouble. What is the cc loss for every .030 milled off. Next question, will angle milling be better for this head. Are their any real performance gains or flow to be had. How much can this reduce the chamber volume. Are their any other areas (problems) to look out for when angle milling. I have a 461 BB Chevy going together using this head & TRW piston L2377. This piston is a forged flat top with two eye brows, chamfered edge at 0 deck. The bores will be relived (unshrouded) to match the gasket. I'm trying to get a minimum of 9.5 compression no more than 10.5. Is this doable.

Thanks for any info you are willing to share,

Ron 92Camaro :beers:
 
#2 ·
I've worked on the 702 castings quite a bit. Opening the chamber will help, especially on the exhaust side. Most BB heads lose 1 cc for every .005" milled so a .030" cut will take 6cc out of the chambers. I would not suggest angle milling. It doesn't have the major benefits on BBC heads. The valves are already canted and you run more into piston to valve issues than anything. You should be able to flat mill them up to about .060" before getting too close to the IN seat (45 angle). You are going to have to correct the intake side of the heads so the manifold will fit properly when cutting more than say .030". Roughly crunching the numbers a 96cc chamber will give you about 9.58:1 compression. a .030" cut or 6cc reduction will bump you to 10:1 and a drop to an 85 cc chamber should put you at and even 10.5:1. These are approximates due to not having true hard numbers, but they should be within a tenth of a point or so.
 
Discussion starter · #3 ·
Mike-CFM said:
I've worked on the 702 castings quite a bit. Opening the chamber will help, especially on the exhaust side. Most BB heads lose 1 cc for every .005" milled so a .030" cut will take 6cc out of the chambers. I would not suggest angle milling. It doesn't have the major benefits on BBC heads. The valves are already canted and you run more into piston to valve issues than anything. You should be able to flat mill them up to about .060" before getting too close to the IN seat (45 angle). You are going to have to correct the intake side of the heads so the manifold will fit properly when cutting more than say .030". Roughly crunching the numbers a 96cc chamber will give you about 9.58:1 compression. a .030" cut or 6cc reduction will bump you to 10:1 and a drop to an 85 cc chamber should put you at and even 10.5:1. These are approximates due to not having true hard numbers, but they should be within a tenth of a point or so.
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Mike,
Thanks for the reply to question. The compression approximates are they for a head that has no chamber grinding (un shrouding of the valves) or bore reliefs. I guess when all done & said, I will cc ever thing. I hopping for 10.5 compression when the grinding dust settles.

Thanks Again,

Ron 92 Camaro :beers:
 
Discussion starter · #6 ·
Mike & FourEightyNine,

Thanks for the return replies and the info. Bottom line is I will cc the chamber when I'm done. I will post the final cc when I get that number and calculate the final compression ratio.

Thanks Again,

Ron 92 Camaro :beers:
 
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